1. Field of the Invention
The invention relates to a friction clutch with a housing, a clutch disk having friction facings, and a diaphragm spring which presses a pressure plate against the clutch disk, contacts a knife edge formed at the pressure plate when the clutch is engaged, and lifts off from the knife edge to release the clutch. The housing and the diaphragm spring are connected so as to be fixed with respect to rotation relative to one another.
2. Description of the Prior Art
A friction clutch of this kind is disclosed, for example, in German reference DE-PS 14 75 332. In order to transmit the torque generated in the drive train, for example, by an internal combustion engine, the clutch disk is pressed on the flywheel by the pressure plate. The contact pressing force is applied by a diaphragm spring which is supported at the clutch housing and which rests with its radial outer area on the knife edge which is provided around the circumference of the pressure plate. For the purpose of disengaging the clutch, the diaphragm spring is pressed in the axial direction so that it lifts off the pressure plate and its radial outer area swivels back in the direction of the clutch housing. Sufficient axial space must be provided so that the spring does not strike against the clutch housing. In the known clutch, this axial space is created by an axial curvature or bulge of the housing.
As a result of increasing optimization of vehicles and the increasing multiplicity of equipment, all structural component parts are required to be as compact and as light as possible. Due to the necessary axial space provided between the pressure plate and the housing, the clutch is correspondingly large in the axial direction. A reduction in the thickness of the pressure plate is usually ruled out because this pressure plate must have a sufficient thermal capacity to store the heat (friction energy) occurring when the clutch is engaged without warping. A reduction in the thickness of the housing is also possible only to a certain degree because, naturally, as the thickness decreases there is an increased risk that the housing will bend.